Giordano Bruno

Giordano Bruno, 1548-1600, was persecuted by the Church
for his heretical views, most notably his belief
that there are countless inhabited worlds around distant stars.
Bruno also advocated the Copernican system.
Unlike Galileo, who grudgingly recanted his views, Bruno ended up
being burned at the stake.

The Heroic Enthusiasts. (Gli Eroici Furori) L. Williams, tr. [1887 and 1889]
The introduction to this translation of
one of Bruno's most celebrated (and cryptic)
works has a good biography of Bruno.